Step 2. Cutting the tiles. Next we want to cut this piece so that it appears to be made of individual tiles. To do this either find the centre or wherever you want to start and from the bottom cut a slice 3/4 of the height, you can do this with scissors, it's much safer and controlled. Then very carefully make another cut alongside the first, as close to the first as possible - you want to be cutting out a tiny sliver so that the two sides don't rub against each other awkwardly - you'll see what I mean when you make the first cut. Continue with the rest of the cuts along the bottom to create the tiles. Remove the little slivers as you go.

Rough up the bottom of the tiles as well by making jagged and varied cuts on them - see the third picture for this.

Step 3. Take the same steps with the next couple of layers, aiming to have them overlap over the tops of the highest points of the tile cuts beneath them. Once you've done this place each layer against the roof base to ensure that they are sufficient to cover the the area in question.

Step 4. Glue them down. You'll have a bit of trouble with pva glue attaching to the plastic I think, but if you do go with pva make sure you rough up the underside of the plastic to grip it better. But the hot glue gun is much much faster; you will have no drying time required

Note the interesting rough surface of the chopping board, I think it's going to be good for dry brushing Artificial

Step 5. After you've done all sides of the roof we're going to cap the edges. To do this cut a rectangular strip, approximately 10mm wide, and in excess of the length you need to cap. Once you've cut it, score down the centre with the scalpel or Stanley knife as I've done in the strip in the picture. Be careful, you don't have much to hold onto when you do this and it is very easy to slip when you're scoring slippery plastic. Keep your fingers away from the path of the blade and go slowly. You don't want to go too deep either, just enough to bend it in the next step.

Step 6. Bend the strip away from the scored side, it should bend fairly easily since you've made a light cut, which will release tension down the centre. Bend it to a 90 degree angle.

Step 7. Cut off the corners at the lower end and the inside edge (to make a 'V') at the top end. Put in place and trim as required. Then glue and put in place. If you don't get it placed right at first you may have to pull it off, remove the now cooled glue and start over. If you put too much on and it oozes out the side, don't worry, keep the cap where it is (if it's sitting in a good spot) and when the glue dries you can carve it off with the scalpel.

Step 8. Create some supports for the upper floor. Let's go back to the larger stone section and put in some 'supporting' beams for the upper floor. For this I used larger chunks of balsa, cut sections out of the foam just below the upper section and going roughly 5-7mm deep. Use some pva glue to stick them in, the hot glue gun is a little tricky to use in holes I found.

Last couple of pics for now, I'm going to try to do some proper plastering on the weekend. You'll notice I also glued a 'light' that I got from a 40k bit box, but you can make your own out of sculpey or beads or both.